Production of alkyl ethers of polyalkylene glycols



United States Patent 3,281,477 PRODUCTEUN @F ALKYL ETHERS 0F PULYALKYLENE GLYCOLS Robert P. Nielsen, Lafayette, Calif, assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed June 30, 1964, Ser. No. 379,361 13 Claims. (Cl. 260-615) This invention relates to a process for the preparation of monoalkylethers of alkylene glycols, especially of polyalkylene glycols. More particularly, the invention relates to the conversion of aliphatic hydrocarbons to hydrocarbyloxy alkanols and hydrocarbyloxy polyalkyleneoxy alkanols and to borate esters thereof.

The oxidation of aliphatic hydrocarbons with oxygen in the presence of boric oxide or boric acid to secondary alkyl borate esters is known; see German Patent No. 552,- 886. The borate esters can be hydrolyzed to yield corresponding secondary alcohols. The ethoxylation of higher aliphatic secondary alcohols in the presence of Friedel- Crafts type catalysts, e.g., boron trifluoride is known; see Carter, U.S. 2,870,220, issued January 20, 1959. Furthermore, borate esters of glycol monoethers have been prepared by reaction of the glycol monoethers with boric acid; see Young, U.S. 3,080,412, issued March 5, 1963. It would be advantageous to alkoxylate borate esters directly to borate esters of glycol (including polyglycol) monoethers which can be hydrolyzed directly to corresponding glycol monoethers.

It is, therefore, a principle object of the present invention to provide a process for oxidizing and alkoxylating aliphatic hydrocarbons to hydrocarbyl polyoxyalkylene alkyanol. A further object of the invention is to provide a process for alkoxylating hydrocarbyl borate esters to corresponding hydrocarbyloxy alkanols and hydrocarbyloxy alkyleneoxy alkanols.

The objects will be better understood and others will be apparent from the description of the invention as given hereinafter.

Now, in accordance with this invention, it has been found that borate esters, particularly secondary alkyl borates produced by controlled oxidation of higher nparafiins in the presence of boric oxide/acid, can be alkoxylated by alkylene oxides, especially lower vicinal alkylene oxides of 2-4 carbon atoms, in the presence of a suitable catalyst, as described hereinafter, to insert one or more oxyalkylene groups in the borate ester to form borate esters of glycol monoethers. These borate esters can be hydrolyzed to the corresponding glycol ethers and boric acid or borate salt. The reactions involved can be represented as follows:

(R 0) B (unbalanced) (I;

The term R-H denotes a saturated aliphatic hydrocarbon of from 1 to 20 carbon atoms which can be normal or branched acyclic or cyclic but preferably essentially free of tertiary hydrogen atoms. Satisfactory results are obtained especially where R is an aliphatic hydrocarbyl of 3 to 20 carbons and preferably of 4 to 16 carbons, especially an alkyl of to 16 carbons. Examples of suitable hydrocarbons include propane, iso-butane, npentane, cyclopentane, n-hexane, cyclohexane, n-octane, cyclooctane, ndodecane, n-tetradecane and n-eicosane. By n is meant any number of oxyalkalene groups of from 1 to 12, more advantageously 2 to 10, and preferably 3 to 8.

323L477 Patented @ct. 25, 19%6 oxides are those wherein there are at least three R'-hydrogens, e.g.,

0 RHC CH;

R being defined as above, and more specifically, ethylene oxide. Other preferred oxides are propylene oxide and l,2-butene oxide.

Boron-containing compounds which are suitable as starting materials, in addition to boron oxide (B 0 include, for example, other boron compounds which are boron acids or give rise to boron acids, such as orthoboric acid and metaboric acid and lower alkyl boric acid esters, e.g., methyl borate and the like.

The borate esters may be prepared by any of the known prior art methods. For example, at atmospheric pressure and at temperature of -170 C., slowly passing a gas containing 33.5% 0 into a reactor containing boric acid and a parafiin hydrocarbon feed in about a 1:3 mole ratio will result in oxidation of the paraffin to secondary alcohol and its esterification to corresponding borate ester. Preferred results can be obtained when partially dehydrated boric acid is used. Further advantages are obtained where the parafiin feed contains less than 0.5% aromatics.

The hydrocarbyloxy(poly)alkyleneoxy alkanols (monoalkyl ethers of polyalkylene glycols) produced by the process of this invention include those containing from 7 to 40 carbons, more advantageously from 9 to 30 and preferably about 12-24 carbons, and more specifically, mono-dodecyl ether of tetraethylene glycol. The desired hydrocarbyloxy polyalkyleneoxy alkanols include lower alkoxy polyalkyleneoxyalkanols, preferably where the polyalkyleneoxyalkanol is polyethyleneoxyethanol or polypropyleneoxy propanol. Further examples of the monoether products of this invention include propyl ether of diethylene glycol, propyl ether of triethylene glycol, nbutyl ether of triethylene glycol, n-hexyl ether of dipropylene glycol, n-dodecyl ether of triethylene glycol, ndodecyl ether of tetraethylene glycol, n-dodecyl ether of dipropylene glycol, n-dodecyl ether of tripropylene glycol, n-dodecyl ether of tetrapropylene glycol and the like.

It has been found that halides, particularly middle halides, and alkoxides, especially lower alkoxides, of metals of Groups II-B, III-B and lV-B and having an atomic number from 12 to 50 are useful catalysts for the alkoxylation of the borate esters with alkylene oxides and of these catalysts, those of zinc, cadmium, aluminum and titanium are preferred; zinc halides, aluminum alkoxides and titanium alkoxides and mixtures thereof are especially useful. Exemplary effective catalysts are: zinc chloride, zinc bromide, zinc methoxide, zinc isopropoxide, aluminum isopropoxide, aluminum methoxide, aluminum chloride, aluminum bromide, titanium tetra-ethoxide, titanium dimethoxide d-ibutoxide and titanium dipropoxide dichloride. Mixtures of the alkoxides of the more acidic metal oxides and the halides of the less acidic metal oxides, e.g., mixtures of aluminum and/or titanium alkoxides and zinc chloride are particularly effective.

The reaction of the borate esters with the alkylene oxides may be advantageously performed in a closed container under pressure from an inert gas, such as nitrogen. The reaction should be performed in the substantial absence of water as the catalyst is inactivated by Water. A

closed container is used to retain volatile solvent which may be utilized during the reaction. The pressure can be varied over a wide range, generally Within the range of p.s.i.g. to 1000 p.s.i.g., with 80 p.s.i.g. to 500 p.s.i.g. being preferred. The pressure, of course, will vary with the temperature at which reaction is performed.

It is advantageous to carry out the process in the presence of a solvent, such as a hydrocarbon, especially a normally liquid saturated aliphatic hydrocarbon alicyclic or cyclic, such as isopentane or cyclohexane. However, the solvent is not indispensable as the alkoxylation can be carried out in the absence of added solvent.

The reaction period for the alkoxylation is not critical but depends on various variable factors which determine the rate of the reaction, including the particular alkylene oxide and borate ester involved, their concentrations in the reaction mixture, the catalyst employed and the temperature. Forty minutes to four hours is usually suitable while about 1 to 2 hours is preferred.

The temperature employed may vary considerably over a broad range depending on the type of reactants involved, it being generally desirable to maintain a temperature in the range of 80 C. to 150 C., with the preferred range being from 100 C. to 130 C.

The alkoxylation catalyst, as described supra, and various mixtures thereof is added to the reaction mixture in catalytic amounts which may vary from, e.g., 0.001% to by weight of the borate ester, with 1.0% to 5.0% being preferred.

The following specific examples of the invention will serve to illustrate more clearly the application of the invention, but the details thereof are not to be construed as limiting the invention.

Example I 90 mole percent of isobutyl borate, 5 mol percent of aluminum isopropoxide and 5 mole percent of zinc chloride were placed in a closed vessel and ethylene oxide in a mole ratio of 9:1 to the isobutyl borate was introduced into the vessel. The reactor was heated slowly to 150 C. over a period of 1 hour. The reactants were maintained at 150 C. and a pressure of 90 p.s.i.g. for an additional hour. Thereafter, the reaction mixture was separated by distillation, with recovery of 63% of the isobutyl borate as a mixture of isobutyl ethoxylated borates containing an average of 4 ethyleneoxy units per isobutyl radical.

Hydrolysis of the ethoxylated borate ester yielded the corresponding mono-butyl ether of polyethylene glycol, i.e., isobutyl ether of tetraethylene glycol.

Example II When 1 mole of tri-(sec-dodecyl)borate is reacted with about 9 moles of propylene oxide, in the presence of aluminum isopropoxide and zinc chloride and the intermediate product hydrolyzed, sec-dodecyl ether of tripropylene glycol is obtained.

Example 111 850 grams of n-dodecane was placed in a closed container. To this vessel was added 29.75 grams of boric anhydride. 21.25 cubic centimeters of a gas containing 3.5% by weight of oxygen was introduced into the vessel. The mixture was heated at 180 C. and 1 atmosphere pressure for about 1 hour. About 20% of the n-dodecane was converted to the corresponding secondary alkyl borate. Subsequent hydrolysis of the sec-dodecyl borate gave an 80% yield of secondary dodecyl alcohol.

When sec-dodecyl borate is reacted with about mol proportions of ethylene oxide at about 150 C. in the presence of 10 mol percent of anhydrous zinc chloride, based on the borate ester, and the resulting reaction mixture hydrolyzed with aqueous sodium hydroxide, a mixture of mono-dodecyl ethers principally of tetra-, pentaand hexa-ethylene glycols is obtained.

I claim as my invention:

1. A process for preparing an alkyl ether of polyalkylene glycol of the formula in which n is a number from 1 to 12, which comprises alkoxylating analkyl borate of the formula (RO) B wherein R is alkyl of 3 to 20 carbon atoms by reaction at to C. and 5 to 1000 p.s.i.g. pressure with an alkylene oxide of 2 to 8 carbon atoms per molecule of the formula wherein each R represents hydrogen or alkyl of 1 to 5 carbon atoms under anhydrous conditions in the presence of 0.001 to 10% weight, based on said alkyl borate, of a catalyst of the group consisting of the middle halides and alkoxides of metals of Groups IIB, IIIB, and IVB having atomic numbers from 12 to 50, and hydrolyzing the alkoxylated borate ester thereby producing the corresponding alkyl ether of polyalkylene glycol.

2. A process in accordance with claim 1 wherein alkyl borate ester having alkyl of 10 to 16 carbon atoms is reacted with ethylene oxide using about 2 to 10 moles of ethylene oxide per alkyl radical of said ester.

3. A process in accordance with claim 1 wherein alkyl ether of 7 to 40 carbon atoms is made by alkoxylating the alkyl borate product of oxidizing a hydrocarbon of from 3 to 20 carbon atoms per molecule in presence of a compound of the group consisting of boric oxide and boric acid.

4. A process in accordance with claim 3 wherein ndodecane is reacted with oxygen and boric oxide, the resulting dodecyl borate ester is reacted with ethylene oxide in about a 4:1 mole ratio to the dodecyl radical in the presence of zinc chloride to form dodecyloxy triethyleneoxyethyl borate which is hydrolyzed to yield monododecyl ether of tetraethylene glycol.

5. A process in accordance with claim 1 wherein R is n-dodecyl.

6. A process in accordance with claim 1 wherein R is isobutyl.

7. A process in accordance with claim 1 wherein the catalyst is a metal lower alkoxide.

8. A process in accordance with claim 7 wherein the metal alkoxide is aluminum isopropoxide.

9. A process in accordance with claim 1 wherein the catalyst is a metal halide.

10. A process in accordance with claim 9 wherein the catalyst is zinc chloride.

11. A process in accordance with claim 3 wherein the boron compound is boric oxide.

12. A process in accordance with claim 3 wherein the alkylene oxide is ethylene oxide.

13. A process in accordance with claim 3 wherein the alkylene oxide is propylene oxide.

No references cited.

LEON ZITVER, Primary Examiner.

H. T. MARS, Assistant Examiner. 

1. A PROCESS FOR PREPARING AN ALKYL ETHER OF POLYALKYLENE GLYCOL OF THE FORMULA 